1. Field of the Invention
The invention relates to systems and methods for generating rotating magnetic fields. In some embodiments, the rotating magnetic fields may be used to acquire NMR spectra.
2. Description of the Related Art
Dipole coupling and chemical shift anisotropy in systems containing molecules that are unable to tumble freely and rapidly (e.g., solid state systems or biological systems containing large biomolecules or cellular or tissue material) results in magnetic field anisotropy that obscures the nuclear magnetic resonance (NMR) spectra of such systems due to line broadening. These line broadening effects can be minimized by spinning the sample about an axis that is at the angle with respect to the Z magnetic field axis in an NMR spectrometer that causes the Z component of the magnetic field due to dipole coupling and chemical shift anisotropy to be zero. This angle is 54.7°, the so called “magic angle,” due to the presence of a 1-3 cos2 θ term in the dipole coupling and chemical shift anisotropy magnetic field equations. Magic angle spinning (MAS) NMR spectroscopy has been used with success for obtaining spectra of solid state samples. However, spinning of biological samples is not feasible. Spinning of ex vivo tissue at the typical 4 to 5 kHz MAS rates can result in damage and component separation due to centrifugal forces during spectrum acquisition. Furthermore, spinning of live animals can be deadly to the animal. Accordingly, there is a need for systems and methods that provide magnetic field rotation through a sample without having to rotate the sample itself.